In the related art, in driving a stepping motor in which three-phase solenoids are star-connected by the use of a plurality of switching means, a technique of switching an excitation pattern of the solenoids from a current excitation pattern to an excitation pattern in which the switching means turned on upstream from the phase grounded and short-circuited is turned off when one phase (solenoid) of the stepping motor is grounded and short-circuited has been proposed (for example, see Patent Document 1). In this technique, the solenoids are protected without cutting a supply of a current (by switching an excitation pattern) through the use of this process.